[Detection of extraneous gases in breath alcohol analysis]

The influence of interfering substances on breath-alcohol measurements is handled by the OIML by giving a list of test gases and prescribing the maximum permissible cross-sensitivity of a measuring system. The expertise of the Federal Health Office for evidential breath analysers prefers an other way to detect interfering substances in expired air. By the use of two measuring systems with different analytical specificity interfering substances as e.g. methanol, isopropanol, aceton, ethylacetat, and toluene cause measured values with a difference which exceeds the limits permitted in the OIML recommendations. The same happens with interfering substances in expired air which are most commonly used by sniffers as e.g. Pattex, Uhu adhesive, or petrol.